First...the launch is on hold while they look at an overheating issue with the Centaur interstage motors. Launch is likely not going to be on-time, but they have a 2-hour launch window, so it still may happen of they get the issue taken care of in time.

Secondly, a correction. The engine on the Atlas V 1st stage is the RD-180, NOT RL-150. Dunno where I got that one.